Air operated double diaphragm pumps are known for pumping a wide variety of substances. In some applications, double diaphragm pumps are utilized to pump chemicals such as acids. In other applications, double diaphragm pumps are utilized to pump comestible substances such as flowable foods and beverages. In these applications, the pumps are typically constructed of non-metallic materials (e.g. polymeric materials) having suitable corrosion resistance, and that are chemically compatible with the substances being pumped.
To operate the double diaphragm pump, an air valve is often provided with a flow control spool valve that regulates the flow of air through the air valve to reciprocatingly drive diaphragms of the double diaphragm pump. The spool valve generally includes a valve housing that defines a valve chamber, and a spool that is received by the valve chamber. The spool includes a plurality of sealing disks that delimit the chamber into two or more subchambers. Inlets and outlets are defined by the housing, and the spool is slidably movable within the valve chamber such that the sealing disks, and therefore the subchambers move along the chamber to provide selective communication between various combinations of the inlets and outlets.
Relatively high pressures are created within the air valves and may cause the valve housing constructed of the non-metallic materials to deform, which can result in valve leakage.